To feed out and hold the lead of a mechanical pencil, in the past, a chuck member has been used. As shown in Japanese Patent Publication No. 2002-321493A, the chuck member is comprised of a chuck and a fastener (fastening ring). The fastener is a hollow substantially cylindrical shape and has a straight inner circumference in the axial line direction. The chuck is split at one end part in the longitudinal direction. The split end part of this chuck enables insertion and withdrawal to and from the fastener and has a tapered outer surface which contacts the inner surface of the fastener when inserted in the fastener. As shown in Japanese Patent Publication No. 2012-158092A, the material of the chuck is typically a metal or plastic.
If the biasing force of a spring causes a chuck to enter a fastener, the tapered outer surface of the chuck receives drag from the inner surface of the fastener, so the split end part of the chuck closes and holds the lead. At the time of writing, in addition to the biasing force of the spring, writing pressure is applied to the chuck through the lead, so the tapered outer surface of the chuck receives a further stronger drag from the inner surface of the fastener. For this reason, the lead is held by the chuck by a stronger holding force, so at the time of writing, the lead can be prevented from sliding back. Note that it is known that a similar advantageous effect can be obtained even by a configuration where the fastener has a tapered inner surface and the chuck has a straight outer surface.